Ultrasonic apparatus, particularly for thermometry

ABSTRACT

A transmitter pulse generator and a receiver detector analyzer electrically communicate with a transmit/receiver ultrasonic transducer which is connected to a lead-in-line having a sensor at one end thereof. Driving pulses generated by the transmitter are applied to the transducer, in consequence ultrasonic pulses propogate down the lead-in-line toward the sensor. Each ultrasonic pulse is reflected partly upon reaching a discontinuity in the sensor and partly upon reaching the termination of the sensor. The reflected pulses or sensor echo pulse pairs are applied to the receiver detector analyzer via the lead-in-line and transducer. A first peak detect and hold circuit and a second peak detect and hold circuit are charged individually to a reference level by the first and second pulse, respectively, of initial sensor echo pairs. The time interval during which the first and second pulses of subsequent sensor echo pairs exceed their correlative reference levels is detected by a first comparator and a second comparator, respectively. The detected time interval is measured by a reference oscillator and a gated counter. The measure interval is presented on a display as an indication of the temperature of the sensor.

United States Patent [1 Gordon et al.

[451 Feb. 20, 1973 [75] Inventors: Bernard M. Gordon, Magnolia;

Leopold Neumann, Lexington; Ivan H. Kirsch, Hyde Park, all of Mass.

[73] Assignee: Gordon Engineering Company,

Wakefield, Mass.

[22] Filed: May 15, 1970 [2]] App]. No.: 37,752

[52] US. Cl. ..73/339 A [51] Int. Cl. ..G0lk 11/24 [58] Field'of Search"73/339 A, 194 A, 67.8

[56] References Cited UNITED STATES PATENTS 3,350,942 11/1967 Peltola..73/339 A OTHER PUBLICATIONS NASA Tech.Brief; Brief Number 68-103l9;August 1968, Ultrasonic Temperature Measuring Device.

Primary Examiner-Louis R. Prince Assistant ExaminerDenis E. CorrAttorney-Morse, Altman & Oates [5 7 ABSTRACT A transmitter pulsegenerator and a receiver detector analyzer electrically communicate witha transmit/receiver ultrasonic transducer which is connected to alead-in-line having a sensor at one end thereof. Driving pulsesgenerated bythe transmitter are applied to the transducer, inconsequence ultrasonic pulses propogate down the lead-in-line toward thesensor. Each ultrasonic pulse is reflected partly upon reaching adiscontinuity in the sensor and partly upon reaching the termination ofthe sensor. The reflected pulses or sensor echo pulse pairs are appliedto the receiver detector analyzer via the lead-in-line and transducer. Afirst peak detect and hold circuit and a second peak detect and holdcircuit are charged individually to a reference level by the first andsecond pulse, respectively, of initial sensor echo pairs. The timeinterval during which the first and second pulses'of subsequent sensorecho pairs exceed their correlative reference levels is detected by afirst comparator and a second comparator, respectively. The detectedtime interval is measured by a reference oscillator and a gated counter.The measure'interval is presented on a display as an indication of thetemperature of the sensor.

Y 13 Claims, 2 Drawing Figures PATENTED 3, 7 l 7. 033

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ULTRASONIC APPARATUS, PARTICULARLY FOR THERMOMETRY BACKGROUND OF THEINVENTION A 1. Field of Invention The present invention relates to hightemperature thermometry and, more particularly, to ultrasonicthermometry.

I 2. Description of the Prior Art Difficulties have been encounteredwith temperature measuring instruments, particularly in nuclearthermometry, due to severe environment conditions, compatibility ofmaterials and geometrical restrictions. The general approach to nuclearthermometry has been based on thermocouples. Basically, the thermocoupleconsists of two dissimilar metallic wires joined at one end. When thejunction end is at a different temperature than the free ends, a voltageproportional to the temperature difference is developed across thejunction. Since such a temperature measurement depends upon electricalproperties, the thermocouple is susceptible to electric noise and lowfrequency vibrations which represent measurement errors. In addition,the stringent requirements placed on the materials and physicalconfiguration of thermocouple sensors makes the use of such sensorsimpractical in certain situations.

SUMMARY OF THE INVENTION An object of the present invention is toprovide an -ultrasonic thermometric apparatus which is characterized bya pulse generator for supplying driving pulses to a transmit/receivertransducer, a lead-in-line having a sensor at one end thereof, areceiver amplifier for accepting sensor echoes reflected by the sensor,a pair of peak detect and hold circuits which are charged to referencethreshold levels by initial sensor echoes, a pair of comparators fordetecting sensor echoes which exceed the reference threshold levels, aprecision reference oscillator and a gated counter for measuring thedetected interpulse period and a display for presenting the-interpulseperiod count as a measure of the temperature of the sensor. Thecombination of pulse generator, transducer,- lead-in-line, sensor,receiver amplifier, peak detect and hold circuits, comparators,reference oscillator and gated counter and display is such as to providea versatile and precise ultrasonic thermometric apparatus which is nothampered by the inherent limitation associated with thermocouples.

The invention accordingly comprises the ultrasonic apparatus possessingthe construction and combination of elements, and arrangements ofcomponents that are exemplified in the following detailed disclosure,the

scope of which will be indicated in the appended claims.

BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of thenature and objects of the present invention, reference should be had tothe following detailed description of the preferred embodiment depictedin the accompanying drawing wherein:

FIG. 1 is a schematic representation, certain mechanical features beingshown in perspective, of an ultrasonic thermometric apparatus embodyingthe present invention; and

FIG. 2 is a block and schematic diagram of the transceiver of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT ture environment 18.Transducer 12, for example a magnostrictive transducer, is energized bya sequence of driving pulses from transceiver 10, whereby a series ofultrasonic pulses propogate along lead-in-line 14 toward sensor 16. Eachof the ultrasonic pulses is reflected partly upon reaching adiscontinuity in sensor 16 and partly upon reaching the termination ofsensor 16, whereby sensor echo pulse pair 22, 24 are reflected backalong lead-in-line 14 for each ultrasonic pulse 20. The sensor echopairs are converted into electrical pulses by transducer 12 and appliedto transceiver 10. As hereinafter delineated, the time duraction of theinterpulse period between each pulse of each sensor echo pair ismeasured in transceiver 10. Since the time duration of the interpulseperiod varies as a function of the temperature of sensor 16, themeasured interpulse period is related directly to the temperature aboutsensor 16.

Now referring to the block and schematic diagram of FIG. 2. Generally,transceiver 10 comprises a cycle control 66 for initiating andcontrolling the measuring process; and internal reference clock 64 forproviding a sequence of time reference pulses; a drive pulse source andsynchronizer 48 for generating a pulse rate synchronized with referenceclock 64; a pulse generator 50 for supplying a sequence of drivingpulses to transducer 12; a blanking delay 52 for generating a blankingpulse to evaluator 58; a receiver amplifier 54 for receiving sensor echopairs from transducer 12; and

inverter amplifier unit 56 for enabling further amplifi cation andpolarity inversion of the sensor echoes as at the output of receiveramplifier 54; evaluators 58 and 60, each responding to one pulse of eachsensor echo pair as at the output of inverter amplifier unit 56; an-

components comprising cycle control 66, drive pulse source'andsynchronizer 48, pulse generator 50,blanking delay 52, receiver 54,inverter amplifier unit 56, evaluators 58 and 60, echo selector 62,clock 64, counter gate 68, counter 75, and display will be described inconjunction with the description of transceiver l0 operation.

In operation, the output of an isolation transformer and full waverectifier network 74 is applied to a trigger 72, whereby pulses ofpredetermined repetition rateare presented at the output of trigger 72.In one example, volts 60 Hertz is applied to the input terminals ofnetwork 74 and the pulses as at the output of trigger 72 have arepetition rate of 120 Hertz. The pulses as at the output of trigger 72are applied to a shaper 76 and a divider 78, in consequence the pulserate of the signals as at the output of shaper 76 and divider 78 and 120Hz and 60 Hz, respectively. Either an external signal or the signal asat the output of shaper 76 or divider 78 is appliedto the .l and K inputterminals of a flip-flop 80 via a pulse rate selector switch 82.Flip-flop 80 is clocked by internal reference clock 64. An inverter 84is connected between the pole of switch 82 and the K input terminal, inconsequence the signal as at the output of minals and its transistion issynchronized with internal reference clock 64. The signal as at theoutput of flipflop 80 is applied to an AND gate 86.

An AND situation is established at the input of AND gate 86 by thesignal as at the output of flip-flop 80 and by the signal as at the poleof switch 90. In one position of switch 90, AND gate 86 is enabledcontinuously allowing through a continuous pulse stream. In the otherposition of switch 90, an external trigger from cycle control 66 isapplied to AND gate 86 through an inverter 306. In this case,'a group oftwelve pulses are allowed through AND gate 86 for each external trigger.The signal as at the output of AND gate 86 is applied to adifferentiating network 308, the differentiated signal being designateda sync signal.

The signal as at the output of AND gate 86 is applied also to anamplifier 92 via a delay flop 94, the pulse width of the signal as atthe output of delay flop 94 being governed by a variable control 96.Driving pulses as at the output of amplifier 92 are applied totransducer 12 via an impedance matching network 98 and transmit coil100, in consequence driving pulse propogate along lead-in-line 14 towardsensor 16. The sensor echo pairs reflected from sensor 16 are applied tothe input of receiver amplifier 54 via transducer 12, a receiver coil104 and a switch 102. Switch 102 is provided with a plurality of inputterminals 106 for selective reception of signals from a plurality ofreceiver coils (not shown). The sensor echo pairs input a limiting andblanking network 108.

Limiting and blanking network 108 is controlled by -the signal as at theoutput of delay flop 94, in conbooster amplifier 118 and 120, echopolarity switches 122 and 123 and echo booster switches 124 and 126. Thepolarity of the sensor echoes as at the input of evaluators 58 and 60 iscontrolled by switches 122 and 123. That is, the polarity of the sensorechoes'as at the output of amplifier 122 is applied directly to theevaluators when switches 122 and 123 are in their first position (asshown) and the opposite polarity of the sensor echoes as at the outputof amplifier 112 is applied to the evaluators via inverter 116 whenswitches 122 and 123 are in their second position. The magnitude of thesensorechoes which input evaluators 58 and 60 is governed by switches124'and 126, respectively, i.e. the magnitude of the sensor echoes as atthe output of switches 122 and 123 is increased when switches 124 and126 are set to pass the signals through amplifiers 118 and 120. Thesensor echoes as at the output of switches 124 and 126 are applied toevaluators 58 and 60, respectively.

Evaluator 58 comprises a peak detect and hold circuit 128, which iscontrolled by an AND gate 138 and a peak reset input signal; a thresholdlevel set 130 for adjusting the magnitude of the threshold level as afraction of the stored peak reference in peak detect and hold circuit128; a comparator 132 for sensing when the input sensor echo exceeds thethreshold level; a control flip-flop 134 for enabling both comparator132 and peak detect and hold circuit 128; and a differentiating network135 at the R input of control flipflop 134. When the inputs to AND gate138 are true, peak detect and hold circuit 128 charges to the peak ofthe sensor echo as at its input. When any of the AND gate 138 inputs arefalse, peak detect and hold circuit 128 retains its previously acquiredpeak reference level. The stored peak reference level established inpeak detect and hold circuit 128 is discharged to a minimum referencevalue by a reset signal applied thereto, in consequence a thresholdlevel safely above the sensor echo line noise level is establishedtherein. Flip-flop 134, set by an end of blanking delay signal" enablescomparator 132 and peak detect and hold circuit 128.

Blanking delay 52 comprises a differentiating trigger network 302 drivenfrom delay flop94 of pulse generator 50 and a delay flop 136. Delay flop136 is triggered by the transmitted pulse and operates to delay theenabling of evaluator 58 until the conclusion of the delay, inconsequence any spurious sensor echos preceeding the desired echo pairare rejected. During the first two sensor echo pairs of a measurement,the previously reset peak detect and hold circuit 128 charges to thepeak value of the first pulse of the first and second sensor echo pairs.The comparator action resets flip-flop 134 at the peak end and thusdisables further action by evaluator 58. During the second ten pulses ofa measurement, peak detect and hold circuit 128 retains its acquiredreference and sets a threshold level for comparator 132 via thresholdlevel set 100. The first pulse of subsequent sensor echo pairs whichexceeds the threshold level is detected by comparator 132. When theselected sensor echo pulse decreases below the threshold level,flip-flop 134 is reset, in consequence evaluator 58 is disabled. In anyevent, flip-flop 134 isreset by the sync signal, whereby a properstarting condition is presented even in a fault condition.

Evaluator 60 is identical to evaluator 58, but is connected to operateon the second pulse of each sensor echo pair. Evaluator 60 comprisespeak detect and hold circuit 140, a threshold level set 142, acomparaselector 62 comprises a delay flop 150 which is controlled by avariable echo selector delay control and enable switch 152; and NANDgate 154 having its output connected to delay flop 150 via an. inverter156; a NOR gate 158 having its output connected to control flip-flop 146via a differentiating network 304 and one of its inputs connected to theoutput of delay flop 150; and a NAND gate 160 having one of its inputsconnected to control flip-flop 134, the other input of NAND gate 160 isconnected to switch 152 and the input of NAND gate 154 via an inverter162. When the switch 152 is in the off position, the signal as at theoutput of NOR gate 158 is such that evaluator 60 enabling is delayeduntil the signal as at the output of delay flop 150 causes NOR gate 158to change state.

For convenience and by way of example, a measuring cycle has beendefined as 12 driving pulses and 24 sensor echoes, each driving pulsebeing reflected as a pair of sensor echoes. The first two echo pairs asat switches 124 and 126 set the threshold level in peak detect and holdcircuits 128 and 140, respectively, the first pulse of each pair settingthe threshold level in peak detect and hold 128 and the second pulse ofeach pair setting the threshold level in peak detector and hold 140. Thefirst and second pulse of each of the remaining sensor echo pairs-areevaluated in comparators 132 and 134, respectively. An output signal isgenerated by evaluator 58 during the period'that the first pulse of theevaluated sensor echo pair exceeds the threshold level establishedtherein and an output signal is generated by evaluator 60 during theperiod that the second pulse of the evaluated sensor echo pair exceedsthe threshold level established therein. The signals as at the outputsof evaluators 58 and 60 input counter gate 68.

Counter gate 68 comprises OR gates 164 and 166; AND gates 168, 170, 172,173 and 174; a flip-flop 176; and dividers 178 and 180. One of theinputs of OR gate 164 is connected to comparator 132 and the other inputis connected to comparator 144. One of the in puts of flip-flop 176 isconnected to comparator 132 via a differentiator 188 and the other inputof flip-flop 176 is connected directly to comparator 144. In thepreferred embodiment of the present invention, divider 178 is a divideby two and divider 180 is a divide by ten. AND gate 170 and divider 178are inputed by the clock pulses generated by clock 64.

Clock 64 is comprised of an oscillator 190, for example a MHz crystaloscillator, and a buffer amplifier 192. During the time that the firstof the pair of the selected sensor echo pulses exceeds the thresholdlevel, 5 MHz pulses as at the output of the divider 178 are applied tocounter 75 via AND gate 174, OR gate 166 and divider 180. Divider 178 isenabled by the signal from comparator 132 via OR gate 164 and AND gate168 and 172. When the first pulse of the pair of the selected sensorecho pairs falls below the threshold level, OR

gate 164 is disabled and flip-flop 176 is set, in consequence AND gate170 is enabled and 10 MHz pulses are applied to counter 75 via AND gate170, OR gate 166 and divider 180. The output signal from evaluator 60,Le. the second of the pair of the selected sensor echo pulses whichexceeds the threshold level, resets flip-flop 176 and also enables ORgate 164, whereby 5 MHz pulses are applied to counter 75. When thesecond of the pair of the selected sensor echo pulses falls below thethreshold level, a counter 183 in cycle control 66 is pulsed advancingits count. In summary, the output signals of evaluators 58 and 60 areprocessed in such a manner that a pulse train of 5 MHz is applied tocounter during the time that respective pulses of selected sensor echopulse pair exceed their threshold level and a pulse train of 10 MHz isapplied to counter 75 during the interpulse period.

Counter 75 comprises high speed counters 184, 186, 188 and 190. Display70 comprises laching registers 192, 194, 196 and 198; decoders 200, 202,204 and 206; numerical indicators 208, 210, 212 and 214; and faultindicator 216. The counters, registers, decoders and numericalindicators are interconnected in such a manner that one counter inputsone register, one register inputs one decoder and one decoder inputs onenumerical indicator; i.e., counter 184 inputs register 192, register 192inputs decoder 200, decoder 200 inputs numerical indicator 208, and soone. The numerical display presented by indicators 208, 210, 212 and 214is the average interpulse period between the first and second pulse ofthe third through twelfth sensor echo pulse pairs. At the end of ameasurement cycle, the data in counters 184, 186, 188 and 190 istransferred to latching registers 192, 194, 196 and 198, respectivelyand is displayed, the correlative decoders and counters are reset toaccept another measurement. Input strobing to registers 192, 194, 196and 198 are controlled by the signal as at the output of cycle control66.

Cycle control 66 comprises counter 183; flip-flop 218, 250 and 256; ANDgates 220, 222, 226, 228 and 254; OR gates 224 and 252; amplifiers 230,232 and 234; and inverters 236 and 238. Counter 183 comprises fiip-flop242, 244, 246 and 248. Counter 183 is incremented at the end of thedetection of each second pulse of each echo sensor pair, hence it'counts the number of driving pulses and controls the 12 pulsemeasurement cycle. Counter 183 is reset to state ZERO by the signal asat the output of amplifier 230 which is inputed by the signal as at theoutput of OR gate 252. At the same time, counters 184, 186, 188 and 190are strobed to registers 192', 194, 196 and 198 by the control signal asat the output of AND gate 222 via amplifier 232. Thereafter, counters184, 186, 188 and 190 are reset. The counter states ZERO and ONE aredetected by OR gate 224 and control peak detect action in evaluators 58and 60, whereby counting by the counter gate is inhibited. During states2 through 11,

AND gate 226 is inputed by either an external trigger 258 or by a groundwhen switch 260 is depressed. Flip- -flop 218 is reset via AND gate 220when counter is in state 11 and the last sensor echo is detected-Flip-flop 218 enables pulse generator 50 to transmit a single 12 pulsegroup.

Flip-flops 254 and 256 constitute a fault detector. Flip-flop 254 is setby a sync pulse (start of transmitted pulse signal) and is reset by thesecond echo detection.

However, during a fault condition flip-flop 254 is not reset. The nextsync pulse will enable AND gate 254 and, if flip-flop 250. is set, itwill energize OR gate 254 reseting counter 183. If AND gate 222 isdisabled, faulty data is not transferred to display 70. At the time ofthe next sync pulse, the state of flip-flop 250 is transferred toflipflop 256, in consequence fault indicator 216 is energized.

The signals as at the output of comparator 146, NOR gate 158 and delayflop 136 are individually applied to the correlative input terminals ofan AND gate 262, the signal as at the output of AND gate 262 being acomposite waveform representing transceiver operation. The signal as atthe output of delay flop 136 is applied to the input of AND gate 262 viaa differentiating network 302. It will be readily appreciated that aplurality of physical properties can be ascertained by the measurementtechnique described herein, for example elastic moduli, Poisson's ratio,metallurgical properties (recovery, recrystallization, grain growth,etc.) chemical properties (carbiding, nitriding, oxidizing, reducing,etc.), nuclear effects and so on.

Since certain changes may be made in the foregoing disclosure withoutdeparting from the scope of, the invention herein involved, it isintended that all matter contained in the above description and depictedin the accompanying drawings be construed in an illustrative and not ina limiting sense.

What is claimed is:

1. An ultrasonic'apparatus comprising:

a. pulse generator means for sending a sequence of driving pulses;

b. transducer means driven'by said pulse generator,

for converting the driving pulses to ultrasonic pulses;

. sensor means electrically communicating with said transducer, saidultrasonic pulses being reflected back by said sensor means as sensorecho pairs; and

receiver means for receiving said sensor echo pulses and analyzingthem'to determine their interpulse period;

. a first evaluator operatively connected to said receiver, a thresholdlevel being established in said first evaluator by the first pulse ofinitial sensor echo pairs, said first evaluator providing an outputsignal when subsequent first-pulses of said sensor echo pairs exceed thethreshold level established therein; and

f. a second evaluator operatively connected to said receiver, athreshold level being established in said second evaluator by the secondpulse of initial sensor pairs, said second evaluator providing an outputsignal when subsequent second pulses of said sensor echo pairs exceedthe threshold level established therein.

. The apparatus as claimed in claim 1 including:

. counter means logically communicating with said first and secondevaluators for measuring the time interval between said first and secondpulse of subsequent sensor echo pairs during which said first and secondpulse exceed their correlative threshold levels and the time duringwhich echoes exceed threshold levels; and

b. display means operatively connected to said counter means forpresenting a numerical display representing the average time intervalbetweensaid first and second pulses of subsequent sensor echo pairsduring which said first and second pulses exceed their correlativethreshold levels.

3. The apparatus as claimed in claim 2 including means for adding anadditional half frequency count.

4. An ultrasonic apparatus comprising:

a. pulse generator means for sending a sequence of driving pulses; 1

b. transducermeans driven by said pulse generator,

for converting the driving pulses to ultrasonic pulses;

c. sensor means electrically communicating with said transducer, saidultrasonic pulses being reflected back by said sensor means as sensorecho pairs;

d. receiver means for receiving said sensor echo pulses and analyzingthem to determine their interpulse period;

e. a blanking delay electrically communicating with said pulse generatorand receiver for selectively blanking said receiver;

f. time reference and counter means for digitizing the interpulseperiod;

g. a first evaluator operatively connected to said receiver, a thresholdlevel being established in said first evaluator by the first pulse ofinitial sensor echo pairs, said first evaluator providing an outputsignal when subsequent first pulses of said sensor echo pairs exceed thethreshold level established therein;

h. a second evaluator operatively connected to said receiver, athreshold level being established in said second evaluator by the secondpulse of initial sensor pairs, said second evaluator providing an,output signal when subsequent second pulses of said sensor echo pairsexceed the threshold level established therein;

i. counter means logically communicating with said first and secondevaluators for measuring the time interval between said first and secondpulse of subsequent sensor echo pairs during which said first and secondpulse exceed their correlative threshold levels and adding an additionalhalf frequency; and

j. display means operatively connected to said counter gate forpresenting a numerical display representing the average time intervalbetween said first and second pulse of subsequent sensor echo pairsduring which said first and second pul- 4 ses exceed their correlativethresholdlevels.

5. The apparatus as claimed in claim 4 including an inverter operativelyconnected to said receiver for selectively controlling the polarity ofthe sensor echo the first pulse of subsequent sensor echo pairs whichexceed the threshold established by said first peak detect and holdmeans;

and said second evaluator comprises:

second peak detect and hold means operatively connected to said receiverfor establishing a threshold level as a function of the second pulse ofinitial sensor echo pairs; and

second comparator means connected to said second peak detect and holdmeans for detecting the second pulse of subsequent sensor echo pairswhich exceed the threshold established by said second peak detect andhold means.

The apparatus as claimed in claim 6 including echo selector meanslogically connected to said second comparator for delaying the enablingof said second comparator during part of the time interval between thefirst and second pulse of said sensor echo pairs.

The apparatus as claimed in claim 7 wherein said transducer is amagnostrictive transducer.

The ultrasonic apparatus as claimed in claim 7 wherein said sensor hasat least two discontinuities, portions of each of said ultrasonic pulsebeing reflected by each of said discontinuities.

10. An ultrasonic apparatus comprising:

a pulse generator for generating a sequence of driving pulses;

transducer means coupled to said pulse generator for converting thedriving pulses to ultrasonic pulses;

. sensor means electrically communicating with said transducer, saidultrasonic pulses being reflected back by said sensor means as sensorecho pairs;

. a receiver coupled to said transducer for receiving said sensor echopulses;

. first peak detect and hold means operatively connected to saidreceiver for establishing a threshold level as a function of the firstpulse of initial sensor echo pairs;

. second peak detect and hold means operatively connected to saidreceiver for establishing a threshold level as a function of the secondpulse of initial sensor echo pairs;

first comparator means electrically connected to said first peak detectand hold means for detecting the first pulse of subsequent sensor echopairs which exceed the threshold established in said first peak detectand hold means;

. second comparator means electrically connected to said second peakdetect and hold means for detecting the second pulse of subsequentsensor echo pairs which exceed the threshold established in said secondpeak detect and hold means;

. counter means logically communicating with said 11. The apparatus asclaimed in claim 10 whereinsaid apparatus includes:

a. a blanking delay electrically communicating with said pulse generatorand receiver for selectively blanking said receiver;

. an inverter amplifier unit operatively connected to said receiver forselectively controlling the polarity of the sensor echo pulses as at theinput of said first and second peak detect and hold means and'first andsecond comparator means;

. a clock operatively connected to said counter means for providing asequence of timing pulses;

. a cycle control logically connected to said counter means and firstand second peak detect and hold means for controlling the sampling timesof said first and second peak detect and hold means; and

. an echo selector logically connected to said second comparator fordelaying the enabling of second comparator during part of the timeinterval between the first and second pulse of said sensor echo pairs.

12. An ultrasonic apparatus comprising:

a. a pulse generator for generating a sequence of driving pulses;

a transducer connected to said pulse generator for converting thedriving pulses to ultrasonic pulses;

. a-sensor operatively connected to said transducer, said sensor havingat least two discontinuities, portions of each of said ultrasonic pulsesbeing reflected by each of said discontinuities as sensor echo pairpulses, said sensor being in a temperature environment; and

. evaluator means connected to said transducer for determining theinterpulse period between each pulse of each of said sensor echo pair,threshold levels being established in said evaluator means by an initialsensor echo pair pulses, said evaluator generating signals whensubsequent sensor echo pair pulses exceed said established thresholdlevels, said interpulse period representing the temperature environmentabout said sensor.

13. An ultrasonic apparatus comprising:

a. pulse generator for generating a sequence of driving pulses;

a transducer connected to said pulse generator for converting thedriving pulses to ultrasonic pulses;

. a lead-in-line connected to said transducer, said ultrasonic pulsespropogating along said lead-in-line;

. a sensor connected to said lead-in-line, said sensor having at leasttwo discontinuities, portions of each of said ultrasonic pulse beingreflected back along said lead-in-line by each of said discontinuitiesas sensor echo pair pulses, said sensor being in a temperatureenvironment;

. a receiver connected to said transducer for receiving said sensor echopulses;

. a blanking delay electrically communicating with said pulse generatorand receiver for selectively blanking said receiver;

. first peak detect and hold'means operatively connected to saidreceiver for establishing a threshold level as a function of the firstpulse of initial sensor echo pairs;

h. second peak detect and hold means operatively connected to saidreceiver for establishing a threshold level as a function of the secondpulse of initial sensor echo pairs;

. first comparator means connected to said first peak detect and holdmeans for detecting the first pulse of subsequent sensor echo pairswhich exceed the threshold established by said first peak detect andhold means;

. second comparator means connected to said peak detect and hold meansfor detecting the second pulse of subsequent sensor echo pairs whichexceed the threshold established by said second peak detect and holdmeans;

. an inverter amplifier unit operatively connected to said receiver forselectively controlling the polarity of the sensor echo pulses as at theinput of said first and second peak detect and hold means and said firstand second comparator means; I

. an echo selector logically connected to said second comparator forblanking said second comparator during part of the time interval betweenthe first and second pulse of said sensor echo pairs;

m. a counter gate logically communicating with said i first and secondcomparators for measuring the time interval between said first andsecond pulse of subsequent sensor echo pairs during which said first andsecond pulse exceed their correlative threshold levels;

n. a clock operatively connected to said counter for

1. An ultrasonic apparatus comprising: a. pulse generator means forsending a sequence of driving pulses; b. transducer means driven by saidpulse generator, for converting the driving pulses to ultrasonic pulses;c. sensor means electrically communicating with said transducer, saidultrasonic pulses being reflected back by said sensor means as sensorecho pairs; and d. receiver means for receiving said sensor echo pulsesand analyzing them to determine their interpulse period; e. a firstevaluator operatively connected to said receiver, a threshold leveLbeing established in said first evaluator by the first pulse of initialsensor echo pairs, said first evaluator providing an output signal whensubsequent first pulses of said sensor echo pairs exceed the thresholdlevel established therein; and f. a second evaluator operativelyconnected to said receiver, a threshold level being established in saidsecond evaluator by the second pulse of initial sensor pairs, saidsecond evaluator providing an output signal when subsequent secondpulses of said sensor echo pairs exceed the threshold level establishedtherein.
 1. An ultrasonic apparatus comprising: a. pulse generator meansfor sending a sequence of driving pulses; b. transducer means driven bysaid pulse generator, for converting the driving pulses to ultrasonicpulses; c. sensor means electrically communicating with said transducer,said ultrasonic pulses being reflected back by said sensor means assensor echo pairs; and d. receiver means for receiving said sensor echopulses and analyzing them to determine their interpulse period; e. afirst evaluator operatively connected to said receiver, a thresholdleveL being established in said first evaluator by the first pulse ofinitial sensor echo pairs, said first evaluator providing an outputsignal when subsequent first pulses of said sensor echo pairs exceed thethreshold level established therein; and f. a second evaluatoroperatively connected to said receiver, a threshold level beingestablished in said second evaluator by the second pulse of initialsensor pairs, said second evaluator providing an output signal whensubsequent second pulses of said sensor echo pairs exceed the thresholdlevel established therein.
 2. The apparatus as claimed in claim 1including: a. counter means logically communicating with said first andsecond evaluators for measuring the time interval between said first andsecond pulse of subsequent sensor echo pairs during which said first andsecond pulse exceed their correlative threshold levels and the timeduring which echoes exceed threshold levels; and b. display meansoperatively connected to said counter means for presenting a numericaldisplay representing the average time interval between said first andsecond pulses of subsequent sensor echo pairs during which said firstand second pulses exceed their correlative threshold levels.
 3. Theapparatus as claimed in claim 2 including means for adding an additionalhalf frequency count.
 4. An ultrasonic apparatus comprising: a. pulsegenerator means for sending a sequence of driving pulses; b. transducermeans driven by said pulse generator, for converting the driving pulsesto ultrasonic pulses; c. sensor means electrically communicating withsaid transducer, said ultrasonic pulses being reflected back by saidsensor means as sensor echo pairs; d. receiver means for receiving saidsensor echo pulses and analyzing them to determine their interpulseperiod; e. a blanking delay electrically communicating with said pulsegenerator and receiver for selectively blanking said receiver; f. timereference and counter means for digitizing the interpulse period; g. afirst evaluator operatively connected to said receiver, a thresholdlevel being established in said first evaluator by the first pulse ofinitial sensor echo pairs, said first evaluator providing an outputsignal when subsequent first pulses of said sensor echo pairs exceed thethreshold level established therein; h. a second evaluator operativelyconnected to said receiver, a threshold level being established in saidsecond evaluator by the second pulse of initial sensor pairs, saidsecond evaluator providing an output signal when subsequent secondpulses of said sensor echo pairs exceed the threshold level establishedtherein; i. counter means logically communicating with said first andsecond evaluators for measuring the time interval between said first andsecond pulse of subsequent sensor echo pairs during which said first andsecond pulse exceed their correlative threshold levels and adding anadditional half frequency; and j. display means operatively connected tosaid counter gate for presenting a numerical display representing theaverage time interval between said first and second pulse of subsequentsensor echo pairs during which said first and second pulses exceed theircorrelative threshold levels.
 5. The apparatus as claimed in claim 4including an inverter operatively connected to said receiver forselectively controlling the polarity of the sensor echo pulses as at theinput of said first and second evaluators.
 6. The apparatus as claimedin claim 5 wherein said first evaluator comprises: a. first peak detectand hold means operatively connected to said receiver for establishing athreshold level as a function of the first pulse of initial sensor echopairs; and b. first comparator means electrically connected to saidfirst peak detect and hold means for detecting the first pulse ofsubsequent sensor echo pairs which exceed the threshold established bysaid first peak detect and hold means; and said second evaluatorcomprises: c. second peak detect and hold means operatively connected tosaid receiver for establishing a threshold level as a function of thesecond pulse of initial sensor echo pairs; and d. second comparatormeans connected to said second peak detect and hold means for detectingthe second pulse of subsequent sensor echo pairs which exceed thethreshold established by said second peak detect and hold means.
 7. Theapparatus as claimed in claim 6 including echo selector means logicallyconnected to said second comparator for delaying the enabling of saidsecond comparator during part of the time interval between the first andsecond pulse of said sensor echo pairs.
 8. The apparatus as claimed inclaim 7 wherein said transducer is a magnostrictive transducer.
 9. Theultrasonic apparatus as claimed in claim 7 wherein said sensor has atleast two discontinuities, portions of each of said ultrasonic pulsebeing reflected by each of said discontinuities.
 10. An ultrasonicapparatus comprising: a. a pulse generator for generating a sequence ofdriving pulses; b. transducer means coupled to said pulse generator forconverting the driving pulses to ultrasonic pulses; c. sensor meanselectrically communicating with said transducer, said ultrasonic pulsesbeing reflected back by said sensor means as sensor echo pairs; d. areceiver coupled to said transducer for receiving said sensor echopulses; e. first peak detect and hold means operatively connected tosaid receiver for establishing a threshold level as a function of thefirst pulse of initial sensor echo pairs; f. second peak detect and holdmeans operatively connected to said receiver for establishing athreshold level as a function of the second pulse of initial sensor echopairs; g. first comparator means electrically connected to said firstpeak detect and hold means for detecting the first pulse of subsequentsensor echo pairs which exceed the threshold established in said firstpeak detect and hold means; h. second comparator means electricallyconnected to said second peak detect and hold means for detecting thesecond pulse of subsequent sensor echo pairs which exceed the thresholdestablished in said second peak detect and hold means; i. counter meanslogically communicating with said first and second comparators formeasuring the time interval between said first and second pulses ofsubsequent sensor echo pairs during which said first and second pulsesexceed their correlative threshold levels; j. display means operativelyconnected to said counter means for presenting a numerical displayrepresenting the average time interval between said first and secondpulses of subsequent sensor echo pairs during which said first andsecond pulses exceed their correlative threshold levels.
 11. Theapparatus as claimed in claim 10 wherein said apparatus includes: a. ablanking delay electrically communicating with said pulse generator andreceiver for selectively blanking said receiver; b. an inverteramplifier unit operatively connected to said receiver for selectivelycontrolling the polarity of the sensor echo pulses as at the input ofsaid first and second peak detect and hold means and first and secondcomparator means; c. a clock operatively connected to said counter meansfor providing a sequence of timing pulses; d. a cycle control logicallyconnected to said counter means and first and second peak detect andhold means for controlling the sampling times of said first and secondpeak detect and hold means; and e. an echo selector logically connectedto said second comparator for delaying the enabling of second comparatorduring part of the time interval between the first and second pulse ofsaid sensor echo pairs.
 12. An ultrasonic apparatus comprising: a. apulse generator for generating a sequence of driving pulses; b. atransducer connected to said pulse generator for convErting the drivingpulses to ultrasonic pulses; c. a sensor operatively connected to saidtransducer, said sensor having at least two discontinuities, portions ofeach of said ultrasonic pulses being reflected by each of saiddiscontinuities as sensor echo pair pulses, said sensor being in atemperature environment; and d. evaluator means connected to saidtransducer for determining the interpulse period between each pulse ofeach of said sensor echo pair, threshold levels being established insaid evaluator means by an initial sensor echo pair pulses, saidevaluator generating signals when subsequent sensor echo pair pulsesexceed said established threshold levels, said interpulse periodrepresenting the temperature environment about said sensor.